Operating instructions

4F5: AC Power Selector Switches
The lower AC panel to the right of the lower
helm wall has three selector switches:
“GENERATORS SELECTOR”
This switch determines which generator
is supplying power, if any...
“AC POWER SELECTOR”
This switch determines whether (1) the generator selected by the “Generators
Selector” is supplying the boat, or (2) the shore power inlet selected by the “Shore
Power Selector is supplying the boat...
“SHORE POWER SELECTOR”
This switch determines which Shore Power receptacle is supplying power, if any.
4F6: AC Reverse Polarity Indicator
Although we tend to think of AC Electricity as having only two conductors, it actually has
three. One of these is called “neutral”; one is “hot”; and one is “ground”, that is, it is supposed
to be the same as the water around the boat and the earth ashore. The vessel and many of
its appliances rely upon these connections having the correct “polarity”, or relationship to one
another and the earth; this is essential to be sure that users of AC equipment do not get a
shock when touching and AC equipment.
Now in a house ashore, it’s easy: We don’t “plug in” the house, for it stays connected
to the utility company all the time! But in a boat when in the harbor, we do plug in using our
Shore Power cords (and sometimes using extension cords). If the outlet to which we plug our
cord or if the cord itself is mis-wired, then these connections can become mixed up, and there
is a significant chance of getting a shock or a chance that running gear outside the boat will be
subject to corrosion because the boat, immersed in sea water, a good conductor of electricity.
To protect the vessel and its crew from such contingencies, a “Reverse Polarity
Warning” light on the lower Generator Control Switch Panel will illuminate when the connection
turned on.
If any “Reverse Polarity” light should illuminate when connecting to Shore
Power, immediately disconnect the cable and contact the harbor master
advising him/her of the problem. Do not risk shock or system damage!
The “Push to Test” button should light the “reversed polarity Bulb” to test it.
4F7: AC Shore Power, Disconnecting & Connecting
The large selector switches on the AC metering panel are used to determine the source
of AC power for the boat (see above). At least one of these switches should be “OFF”
whenever you are connecting or disconnecting the boat to shore. This is true so that you do
not draw an arc from the plug due to the load of the boat on the connector’s pins: such an arc
will burn the contacts and eventually cause them to overheat when in use, creating a fire
hazard.
Once connected to shore power, monitor the AC voltmeter and ammeter — both
Section 4F: Electrical Systems, AC 4.12